A cutting tool is known which includes a base member of cemented carbide, cermet, or ceramics, and a coating layer located on a surface of the base member. This type of cutting tool is generally called coated tool. For example, a titanium carbonitride (TiCN) layer and an aluminum oxide (Al2O3) layer are known as a coating layer.
The cutting tool has a greater opportunity to be used under severe cutting conditions, such as heavy interrupted cutting, along with the recent higher efficiency in a cutting process. A cutting edge is susceptible to large impact during the heavy interrupted cutting. The coating layer is subjected to large impact, and chipping and peeling of the coating layer are likely to occur under the severe cutting conditions. The coating layer therefore needs improvement in fracture resistance in addition to wear resistance.
In Japanese Unexamined Patent Publication No. 9-174304 (Patent Document 1), an intermediate layer composed of needle-shaped particles when viewed from a cross-section direction exists at an interface between a titanium carbonitride layer and an aluminum oxide layer deposited on a surface of the titanium carbonitride layer. The existence of the intermediate layer contributes to improving fracture resistance of a cutting tool described in Patent Document 1.
However, there is still demand for further improved wear resistance and fracture resistance of the coating layer.